1. Field of Invention
This invention finds use in the field of liquid purification, such as water treatment. More particularly, this invention relates to fibers coated with metal oxides for use in water purification.
2. Background
Metal oxides and hydroxides in general, and specifically the oxides and hydroxides of aluminum, iron, titanium, zirconium, manganese, copper, zinc, vanadium, nickel, platinum and palladium are effective adsorbents for the removal of heavy metals and other contaminants from liquid streams. These oxides have a very high adsorbent capacity for the removal of the metals, but the rate of removal of the metals is often limited by the physical size of the particles of the oxides and hydroxides required for good flow characteristics.
The problem of flow restrictions when using very small particles is well known. In porous structures such as carbon blocks, it is desirable to use small particles of metal oxides or hydroxides, zeolites or other materials for the purpose of removal of metals and other contaminants from liquid streams. However, if the particles are smaller than about 20 microns, they are easily eluted from the porous structure and into the treated liquid stream. One solution is the binding of small particles to fibers, as has been shown in U.S. Pat. Nos. 4,190,532 (limited to ion exchange resins with fibers having a negative charge, prior to application), 4,238,334 (limited to materials of certain charges) and 5,346,624 (limited to materials as a precoat). U.S. Pat. No. 6,265,064 plates titanium dioxide on a natural organic fiber, but such process suffers from several inherent problems. U.S. Pat. No. 4,935,265 uses coatings of metal carboxylates and metal alkoxides to strengthen fibers. Cuno U.S. Pat. No. 5,928,588 uses fibers in the production of carbon blocks to improve green strength of the blocks, but there is no mention of the use of fibers coated with materials for use in purification and other desired properties.